Communications terminal, and a method for selecting a transmit antenna for a transmission to a radio communications network

ABSTRACT

A communications terminal may include: a plurality of antennas; and a selection circuit configured to select at least one antenna of the plurality of antennas as a transmit antenna for a transmission to a radio communications network, wherein a selection of the transmit antenna may be based on a selection criterion.

TECHNICAL FIELD

Various aspects relate to a communications terminal and a method forselecting a transmit antenna for a transmission to a radiocommunications network.

BACKGROUND

Devices operating in, for example, a radio communications network, maybe equipped with two or more antennas. Signals may not be transmittedand/or received on the two or more antennas of the device with, forexample, identical data throughputs and/or powers. In other words, thetwo or more antennas of the device may exhibit differences (e.g. in datathroughputs and/or transmit and/or receive powers). For example, thedifferences among the antennas may be a result of, for example, anobject (e.g. a hand and/or a head of a human user) covering at least oneantenna of the device. By way of another example, the differences amongthe antennas may be a result of, for example, the two or more antennashaving different polarizations and/or alignments. Differences among theantennas may be exploited in order to, for example, increase datathroughput of the device and/or to conserve battery consumption by thedevice and/or to optimize the use of network resources (e.g. time slot,frequency bandwidth, channel access code, etc.) in the radiocommunications network.

SUMMARY

A communications terminal is provided, which may include: a plurality ofantennas; and a selection circuit configured to select at least oneantenna of the plurality of antennas as a transmit antenna for atransmission to a radio communications network, wherein a selection ofthe transmit antenna may be based on a selection criterion.

A method for selecting a transmit antenna for a transmission to a radiocommunications network is provided, which may include: determiningwhether a selection criterion is fulfilled; and selecting at least oneantenna of the plurality of antennas as the transmit antenna in case theselection criterion is determined to be fulfilled.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, like reference characters generally refer to the sameparts throughout the different views. The drawings are not necessarilyto scale, emphasis instead generally being placed upon illustrating theprinciples of the invention. In the following description, variousaspects of the invention are described with reference to the followingdrawings, in which:

FIG. 1 shows a communications system.

FIG. 2 shows a block diagram of a terminal.

FIG. 3 shows a block diagram of a communications terminal including aplurality of antennas and a selection circuit.

FIG. 4 shows a detailed block diagram of a communications terminalincluding a plurality of antennas, a selection circuit, a receiver, atransmitter, and a determining circuit.

FIG. 5 shows various examples that illustrate a dependency of athreshold on a magnitude of a value.

FIG. 6 shows a method for selecting a transmit antenna for atransmission to a radio communications network.

DESCRIPTION

The following detailed description refers to the accompanying drawingsthat show, by way of illustration, specific details and aspects in whichthe invention may be practised. These aspects are described insufficient detail to enable those skilled in the art to practice theinvention. Other aspects may be utilized and structural, logical, andelectrical changes may be made without departing from the scope of theinvention. The various aspects are not necessarily mutually exclusive,as some aspects can be combined with one or more other aspects to formnew aspects. Various aspects are described for structures or devices,and various aspects are described for methods. It may be understood thatone or more (e.g. all) aspects described in connection with structuresor devices may be equally applicable to the methods, and vice versa.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration”. Any aspect or design described herein as“exemplary” is not necessarily to be construed as preferred oradvantageous over other aspects or designs.

The term “radio communications network” is used herein to refer to aradio communications system configured in accordance with the networkarchitecture of any one of, or any combination of, LTE (Long TermEvolution) cellular communications technology, UMTS (Universal MobileTelecommunications System) cellular communications technology which mayinclude the system enhancement HSPA (High Speed Packet Access), GSM(Global System for Mobile Communications) cellular communicationstechnology which may include system enhancements General Packet RadioSystem (GPRS) and Enhanced Data rates for GSM Evolution (EDGE) andCDMA2000 (Code Division Multiple Access) cellular communicationstechnology, although other radio communications technology may bepossible as well.

The terms “radio communications network”, “network”, “radio network”,“cellular network”, “radio network communications system”, “cellularnetwork communications system”, “cellular radio communicationstechnology”, “cellular communications system” and “radio communicationssystem” may refer to the same logical entity and may be usedinterchangeably throughout the entire description.

The word “circuit” is used herein to mean any kind of a logicimplementing entity, which may be special purpose circuitry or processorexecuting software stored in a memory, firmware, or any combinationthereof. Thus, in one or more examples, a “circuit” may be a hard-wiredlogic circuit or a programmable logic circuit such as a programmableprocessor, e.g. a microprocessor (e.g. a Complex Instruction SetComputer (CISC) processor or a Reduced Instruction Set Computer (RISC)processor). A “circuit” may also be a processor executing software, e.g.any kind of computer program, e.g. a computer program using a virtualmachine code such as e.g. Java. Different circuits can thus also beimplemented by the same component, e.g. by a processor executing twodifferent programs.

FIG. 1 shows a communications system 100.

The communications system 100 may include a communications terminal 102(which may also be referred to as a terminal 102), and at least onenetwork component 106 a, 106 b, 106 c, which may be part of a radiocommunications network 104. In other words, the at least one networkcomponent 106 a, 106 b, 106 c may be a component of the radiocommunications network 104.

Only one terminal 102 is shown as an example, however the number ofterminals may be greater than one, and may, for example, be two, three,four, five, six, seven, eight, nine, or on the order of tens, hundredsof, or even more terminals. In like manner, only three networkcomponents 106 a, 106 b, 106 c are shown as an example, however thenumber of network components may be one, two and may be more, forexample, four, five, six, seven, eight, nine, or on the order of tens,hundreds of, or even more network components.

The communications system 100 and/or the radio communications network104 may be configured in accordance with the network architecture of anyone of, or any combination of, LTE (Long Term Evolution) cellularcommunications technology, UMTS (Universal Mobile TelecommunicationsSystem) cellular communications technology, GSM (Global System forMobile Communications) cellular communications technology, and CDMA2000(Code Division Multiple Access) cellular communications technology,although other cellular communications technology may be possible aswell.

The terminal 102 may include, or may be, a UE (user equipment) equippedwith a SIM (Subscriber Identity Module) running on a UICC (UniversalIntegrated Circuit Card), a computer (e.g. a laptop equipped with, forexample, a wireless radio connection, such as, for example, a 3G (3^(rd)generation) radio connection), or any other equipment that may beconfigured to connect to a radio communications network.

The terminal 102 (e.g. a UE) may be within the area of coverage of theradio communications network 104, such as, for example, a PLMN (PublicLand Mobile Network). The area of coverage of the radio communicationsnetwork 104 may be the aggregate result of the coverage of the at leastone network component 106 a, 106 b, 106 c of the radio communicationsnetwork 104. In other words, each network component of the at least onenetwork component 106 a, 106 b, 106 c of the radio communicationsnetwork 104 may have a respective area of coverage, and an aggregationof the respective areas of coverage may determine the area of coverageof the radio communications network 104. By way of an example, the areaof coverage (which may also be referred to as “the region of coverage”)of the radio communications network 104 shown in FIG. 1 may at least bethe aggregate result of the coverage of the network components 106 a,106 b, and 106 c, and other network components belonging to the radiocommunications network 104 (other network components (e.g. basestations) are not shown in FIG. 1).

At least one of the network components 106 a, 106 b, 106 c may include,or may be, a base station, a NB (Node B), an eNB (Evolved Node B), aHome NB, a traditional NB, and a wireless router, although other networkcomponents may be possible as well.

In FIG. 1, the terminal 102 may be configured to transmit an uplink (UL)signal 110 at a particular power. An uplink (UL) may refer to aconnection (e.g. a communications connection) from the terminal 102towards at least one network component (e.g. the network component 106b) of the radio communications network 104. Accordingly, the UL signal110 may include, or may be, a signal transmitted from the terminal 102(e.g. a UE) to at least one network component (e.g. the networkcomponent 106 b, for example a base station) of the radio communicationsnetwork 104.

In FIG. 1, the at least one network component 106 a, 106 b, and 106 c(e.g. base station) may be configured to transmit a downlink (DL) signalat a particular power. A downlink (DL) may refer to a connection (e.g. acommunications connection) from at least one of the network components106 a, 106 b, 106 c of the radio communications network 104 towards theterminal 102. Accordingly, a DL signal may include, or may be, a signaltransmitted from the at least one network component 106 a, 106 b, 106 c(e.g. base station) to the terminal 102 (e.g. a UE). By way of anexample, the network component 106 a may be configured to transmit a DLsignal 108 a; the network component 106 b may be configured to transmita DL signal 108 b; and the network component 106 c may be configured totransmit a DL signal 108 c. The respective DL signals 108 a, 108 b, 108c transmitted by the at least one network component 106 a, 106 b, and106 c may, for example, cover a particular geographical area.

The geographical area covered by a network component (i.e. the region ofcoverage of a network component) of the at least one network component106 a, 106 b, or 106 c may be substantially (namely, approximately)represented by a cell (which may also be referred to as a “radio cell”).By way of an example, the region of coverage of the network component106 a may be substantially represented by a cell 105 a; the region ofcoverage of the network component 106 b may be substantially representedby a cell 105 b; and the region of coverage of the network component 106c may be substantially represented by a cell 105 c. Accordingly, theregion of coverage of the radio communications network 104 may berepresented by at least one cell, or by a tessellation of two or morecells, where each cell may be an approximation of the area of coverageof a network component (e.g. base station) of the radio communicationsnetwork 104. By way of an example, area of coverage of the radiocommunications network 104 may represented by the tessellation of cells105 a, 105 b, and 105 c.

Whilst a respective cell 105 a, 105 b, 105 c may be an approximation ofthe area of coverage of a respective network component 106 a, 106 b, 106c, there may be geographical regions that may be served by more than onenetwork component. By way of an example, the geographical region oneither side of a boundary formed by a line joining points 1A and 1Bshown in FIG. 1 may be served by the network component 106 a or thenetwork component 106 b, or both; the geographical region on either sideof a boundary formed by a line joining points 1B and 1C may be served bythe network component 106 a or the network component 106 c, or both; andthe geographical region on either side of a boundary formed by a linejoining points 1B and 1D may be served by the network component 106 b orthe network component 106 c, or both.

When the terminal 102 is initially switched off, there may be noconnection between the terminal 102 and the radio communications network104. For example, there may not exist a connection (e.g. acommunications connection, e.g. a communications channel) between theterminal 102 and the network component 106 b (or any of the othernetwork components 106 a, 106 c) shown in FIG. 1 when the terminal 102is powered down. Accordingly, a terminal 102 that is switched off maynot have connectivity to a communications service and/or networkresource (e.g. time slot, frequency bandwidth, channel access code,etc.) delivered by the radio communications network 104 and/or thenetwork component 106 b.

However, when the terminal 102 is turned on within and/or near the areaof coverage of the radio communications network 104, the terminal 102may search for and/or identify and/or select a network component of theat least one network component 106 a, 106 b, 106 c of the radiocommunications network 104. By searching for and/or identifying and/orselecting a network component (e.g. a base station), the terminal 102may establish a connection (e.g. communications connection) with theradio communications network 104 in order to, for example, use acommunications service and/or network resource (e.g. time slot,frequency bandwidth, channel access code, etc.) delivered by the radiocommunications network 104 and/or at least one of the network components106 a, 106 b, 106 c.

A communications connection with the radio communications network 104may be established by means of, for example, establishing at least onecommunications channel between the terminal 102 and at least one of thenetwork components 106 a, 106 b, 106 c. The at least one communicationschannel established between the terminal 102 and at least one of thenetwork components 106 a, 106 b, 106 c may include at least one ULchannel (e.g. a channel from the terminal 102 to at least one of thenetwork components 106 a, 106 b, 106 c) and/or at least one DL channel(e.g. a channel from at least one of the network components 106 a, 106b, 106 c to the terminal 102).

The number of network components 106 a, 106 b, 106 c used to establish acommunications channels may, for example, depend on the radiocommunications network 104. In a radio communications network 104 whichmay, for example, be a hard handoff system, there may be acommunications channel established between the terminal 102 and one ofthe network components (e.g. the network component 106 b). If, forexample, the terminal 102 is mobile (i.e. moving), the link to, forexample, the network component 106 b established through thecommunications channel may be terminated before, or as, the terminal 102is transferred to a new network component (e.g. the network component106 a). In other words, the terminal 102 may be linked to no more thanone network component at a given time.

In a radio communications network 104 which may, for example, be a softhandover (SHO) system (e.g. in a CDMA and/or UMTS system), the terminal102 may be connected to two or more network components at a time (e.g.the network components 106 a and 106 b). The network component with, forexample, the highest relative strength seen from the terminal 102 may begiven control of the terminal 102.

A communications channel between the terminal 102 and at least one ofthe network components 106 a, 106 b, 106 c may be assumed to bereciprocal. In other words, a quality of an UL channel between theterminal 102 and a network component (e.g. as measured by a criterion,e.g. dropped call rate, ratio of number of data received indicators(ACKs) to number of data not received indicators (NACK)) may be at leastsubstantially equal to a quality of a DL channel between the networkcomponent and the terminal 102. For example, as shown in FIG. 1, thequality of an UL channel between the terminal 102 and the networkcomponent 106 b may be substantially equal to the quality of a DLchannel between the network component 106 b and the terminal 102.

In a TDD (time-division duplexing) scheme where the UL channel and theDL channel use identical frequencies or frequency bands, the quality ofthe DL channel may be identical to the quality of the UL channel. In aFDD (frequency-division duplexing) scheme where the UL channel and theDL channel use different frequencies or frequency bands separated by asmall frequency shift, the UL channel and the DL channel may be highlycorrelated. Accordingly, the quality of the DL channel may beapproximately equal to the quality of the UL channel. There may, forexample, be small differences caused by, e.g. slightly different fadingcharacteristics on the DL channel as compared to the UL channel.However, the differences may not yield a significant difference in thequality of the UL channel and the quality of the DL channel. Forexample, delay spread of a path delay profile of the DL channel may notdiffer much from the UL channel. Accordingly, there may not be asubstantial difference in the quality of the UL channel and the DLchannel (e.g. as measured by a criterion, e.g. dropped call rate, ratioof number of data received indicators (ACKs) to number of data notreceived indicators (NACK)).

FIG. 2 shows a block diagram of the terminal 102.

Reference signs in FIG. 2 that are the same as in FIG. 1 denote the sameor similar elements as in FIG. 1. Thus, those elements will not bedescribed in detail again here; reference is made to the descriptionabove. Differences between FIG. 2 and FIG. 1 are described below.

The terminal 102 may include a plurality of antennas 202 a, 202 b and areceiver 204. Only two antennas 202 a, 202 b are shown as an example ofthe plurality of antennas, however the number of antennas may be greaterthan two, and may, for example, be three, four, five, six, seven, eight,nine, or on the order of tens, or even more antennas.

During operation of the terminal 102, signals may not be transmittedand/or received on plurality of antennas 202 a, 202 b with, for example,identical data throughputs and/or powers. In other words, the pluralityof antennas 202 a, 202 b may exhibit differences (e.g. in datathroughputs and/or transmit and/or receive powers). For example, thedifferences among the antennas of the plurality of antennas 202 a, 202 bmay be a result of, for example, an object (e.g. a hand and/or a head ofa human user) covering at least one antenna of the plurality of antennas202 a, 202 b. For example, a hand of a user of the terminal 102 maycover the antenna 202 b, whilst the antenna 202 a may not be covered bythe hand and/or head of the user, or blocked in any way, thus resultingin a difference in, for example, data throughputs and/or transmit and/orreceive powers among the antennas of the plurality of antennas 202 a,202 b. By way of another example, the differences among the antennas ofthe plurality of antennas 202 a, 202 b may be a result of, for example,antennas of the plurality of antennas 202 a, 202 b having differentpolarizations and/or alignments. Accordingly, the polarizations and/oralignments of some antennas of the plurality of antennas 202 a, 202 bmay be better than others, thus resulting in a difference in, forexample, data throughputs and/or transmit and/or receive powers amongthe antennas of the plurality of antennas 202 a, 202 b.

In a DL transmission where a DL signal 208 (e.g. which may include atleast one of DL signals 108 a, 108 b, 108 c shown in FIG. 1) istransmitted from at least one of the network components 106 a, 106 b,106 c, the terminal 102 may, for example, concurrently use at least twoantennas of the plurality of antennas 202 a, 202 b to receive a DLsignal. In other words, the terminal 102 may exhibit parallel receptionof the DL signal 208 with multiple antennas 202 a, 202 b in the DL.Stated in yet another way, the terminal 102 may receive the DL signal208 using two or more of its antennas at the same time. In the exampleshown in FIG. 2, the terminal 102 receives the DL signal 208 using theantennas 202 a and 202 b at the same time. In other words, the terminal102 may use receive diversity.

In a DL transmission from the radio communications network 104 (e.g.from at least one of the network components 106 a, 106 b, 106 c), theabove-described differences among the antennas of the plurality ofantennas 202 a, 202 b may be considered. For example, the terminal 102may include the receiver 204, which may, for example, select and/orcombine the DL signal 208 received on each antenna of the plurality ofantennas 202 a, 202 b. For example, the receiver 204 may include, or maybe, one or more rake receivers. Accordingly, the receiver 204 may, forexample, be configured to perform at least one of selection combining,equal combining, switched combining or maximal ratio combining, althoughother combination schemes may be possible as well. By way of anotherexample, the receiver 204 may select the DL signal 208 received on atleast one “better” antenna among the plurality of antennas 202 a, 202 b,for example, when DL channel conditions are good. The at least one“better” antenna may be regarded as “better” based on some criterion,e.g. SNR (signal-to-noise ratio). Other antennas of the plurality ofantennas 202 a, 202 b which do not meet the criterion may, for example,be turned off during reception of the DL signal 208. Hence, the DLsignal 208 may not be received by antennas which do not meet thecriterion.

On the other hand, an UL transmission from the terminal 102 to the radiocommunications network 104 (e.g. to at least one of the networkcomponents 106 a, 106 b, 106 c) may only use one antenna of theplurality of antennas 202 a, 202 b at a given time. For example, theterminal 102 shown in FIG. 2 may transmit the UL signal 110 using onlythe antenna 202 a, whilst antenna 202 b may be turned off (e.g. notused) during an UL transmission of the UL signal 110. The antenna 202 aused for an UL transmission may, for example, be referred to as the mainantenna.

In contrast to reception of a DL signal 208 where a selection of atleast one antenna of the plurality of antennas 202 a, 202 b may beperformed by, for example, the receiver 204 (e.g. by means of combiningand/or selection of an antenna), the terminal 102 may not be configuredto perform a selection of antennas in an UL transmission. For example,the terminal 102 may not be configured to select an antenna of theplurality of antennas 202 a, 202 b to transmit the UL signal 110. Forexample, the antenna 202 a shown in FIG. 2 may, for example, bearbitrarily fixed as the main antenna by the manufacturer. Therefore,the terminal 102 may not, for example, actually perform a selection ofthe antenna 202 a to transmit the UL signal 110. For example, theterminal 102 may be configured (e.g. preprogrammed and/or hardwired) touse only antenna 202 a as a transmit antenna in an UL transmission.Furthermore, selection of at least one antenna of the plurality ofantennas 202 a, 202 b by the terminal 102 to transmit the UL signal 110may be difficult. For example, the terminal 102 may not have explicitknowledge of a quality of reception (e.g. SNR) at an antenna of the atleast one network component 106 a, 106 b, 106 c (e.g. NB). Accordingly,the terminal 102 may not have a metric which may be used to select anantenna of the plurality of antennas 202 a, 202 b for an ULtransmission. In addition, the terminal 102 may be configured totransmit the UL signal 110 with only one antenna, and not with two ormore antennas in parallel, namely, at the same time. In other words, theterminal 102 may not be configured to perform a parallel transmitprocedure in a UL transmission where the UL signal 110 is transmittedconcurrently on two or more antennas of the plurality of antennas 202 a,202 b. This may be in contrast to the parallel reception with theplurality of antennas 202 a, 202 b in the DL, where the DL signal 208may be received concurrently on two or more antennas of the plurality ofantennas 202 a, 202 b.

In summary, the terminal 102 may not be configured or able to select anantenna of the plurality of antennas 202 a, 202 b to transmit the ULsignal 110. In addition, or separately, the terminal 102 may not beconfigured to concurrently use more than one antenna of the plurality ofantennas 202 a, 202 b in an UL transmission.

Accordingly, use of an antenna (e.g. antenna 202 a) with, for example, apoor data throughput and/or poor polarization and/or alignment in an ULtransmission may result in poor reception (or non-reception) of the ULsignal 110 by the radio communications network 104. This may reduce anuplink throughput in the terminal 102 and/or the radio communicationsnetwork 104. The radio communications network 104 (e.g. a UMTS system)may require the terminal 102 to retransmit the UL signal 110 in case theUL signal 110 is not received by it (e.g. by at least one of the networkcomponents 106 a, 106 b, 106 c). For example, the radio communicationsnetwork 104 may require the terminal 102 to retransmit the UL signal 110at a higher transmit power and/or to retransmit the UL signal 110 untilthe radio communications network 104 received the UL signal 110.Consequently, retransmission of the UL signal 110 by the terminal 102,e.g. due to use of an antenna with a poor performance, may increase apower consumption of the terminal 102, and may consequently reduce astand-by time of the terminal 102. In addition, retransmissions maywaste valuable network resources (e.g. time slot, frequency bandwidth,channel access code, etc.) of the radio communications network 104,which may otherwise have been allocated for other uses.

Accordingly, there may be a need to enable or allow the terminal 102 toselect an antenna of the plurality of antennas 202 a, 202 b to transmita signal (e.g. the UL signal 110). Separately, or in addition, there maybe a need to enable the terminal 102 to use more than one antenna of theplurality of antennas 202 a, 202 b in a transmission (e.g. in an ULtransmission).

Enabling a terminal to select and/or use at least one antenna totransmit a signal may have an effect of increasing a stand-by time ofthe terminal.

Enabling a terminal to select and/or use at least one antenna totransmit a signal may have an effect of reducing power consumption inthe terminal.

Enabling a terminal to select and/or use at least one antenna totransmit a signal may have an effect of increasing uplink throughput inthe terminal and/or a radio communications network.

Enabling a terminal to select and/or use at least one antenna totransmit a signal may have an effect of optimizing the use of networkresources (e.g. time slot, frequency bandwidth, channel access code,etc.) of a radio communications network and/or of a radio cell.

FIG. 3 shows a block diagram of a communications terminal 300 includinga plurality of antennas 302 a, 302 b and a selection circuit 304.

The communications terminal 300 may, for example, be able to select atleast one antenna to transmit a signal. For example, the communicationsterminal 300 may select antenna 302 a and/or antenna 302 b to transmit asignal (e.g. to a radio communications network).

Only two antennas 302 a, 302 b are shown as an example of the pluralityof antennas, however the number of antennas may be greater than two, andmay, for example, be three, four, five, six, seven, eight, nine, or onthe order of tens, or even more antennas.

The communications terminal 300 may include, or may be, a UE (userequipment) equipped with a SIM (Subscriber Identity Module) running on aUICC (Universal Integrated Circuit Card), a computer (e.g. a laptopequipped with, for example, a wireless radio connection, such as, forexample, CDMA2000 and/or UMTS), or any other equipment that may beconfigured to connect to a radio communications network.

The selection circuit 304 may, for example, be configured to select atleast one antenna of the plurality of antennas 302 a, 302 b as atransmit antenna for a transmission to a radio communications network.The selection of the transmit antenna by the selection circuit 304 may,for example, be based on a selection criterion (see description below inrespect of FIG. 4).

For example, antenna 302 a and/or antenna 302 b may be selected as thetransmit antenna or transmit antennas for a transmission of, forexample, an UL signal, to a radio communications network (e.g. to atleast one network component (e.g. eNB, base station, etc.) of the radiocommunications system). By way of another example, the antenna 302 a ofthe communications terminal 300 may, for example, be a transmit antennafor a current (e.g. present) transmission to a radio communicationsnetwork. In such an example, the selection circuit 304 may, for example,switch the transmit antenna from antenna 302 a to antenna 302 b. Inother words, the selection circuit 304 may be configured to select atleast one antenna of the plurality of antennas 302 a, 302 b as atransmit antenna for a subsequent transmission (e.g. UL transmission) toa radio communications network.

As described above, there may be differences among the plurality ofantennas 302 a, 302 b (e.g. differences in data throughputs and/ortransmit power). The selection circuit 304 may use these differencesamong the plurality of antennas 302 a, 302 b to select a transmitantenna that may, for example, result in a more efficient and/or a morereliable transmission from the communications terminal 300 to a radiocommunications network.

An effect provided by the communications terminal 300 may be increase instand-by time of the communications terminal 300.

An effect provided by the communications terminal 300 may be reductionin power consumption in the communications terminal 300.

An effect provided by the communications terminal 300 may be increaseduplink throughput in the communications terminal 300 and/or in a radiocommunications network to which the communications terminal 300transmits a signal.

An effect provided by the communications terminal 300 may be optimizeduse of network resources (e.g. time slot, frequency bandwidth, channelaccess code, etc.) of a radio communications network to which thecommunications terminal 300 transmits a signal.

An effect provided by the communications terminal 300 may be substantialreduction or removal of a need for feedback or control from a networkcomponent to select a transmit antenna, thus allowing selection of atransmit antenna in the communications terminal 300 to be standardindependent.

FIG. 4 shows a detailed block diagram of the communications terminal 300including the plurality of antennas 302 a, 302 b, the selection circuit304, a receiver 402, a transmitter 404, and a determining circuit 406.

Reference signs in FIG. 3 that are the same as in FIG. 2 denote the sameor similar elements as in FIG. 2. Thus, those elements will not bedescribed in detail again here; reference is made to the descriptionabove. Differences between FIG. 3 and FIG. 2 are described below.

As described above, the selection of the transmit antenna by theselection circuit 304 may be based on a selection criterion. Theselection criterion may be based on signals and/or information and/ormessages provided to a determining circuit 406. The determining circuit406 may determine whether the selection criterion is fulfilled and maybe configured to provide a selection trigger to the selection circuit304 in case the selection criterion is fulfilled. The selection triggermay trigger the selection of the transmit antenna by the selectioncircuit 304. Provision of the selection trigger by the determiningcircuit 406 to the selection circuit 304 is indicated as arrow 406 a inFIG. 4. The description that follows describes the selection criterion,how the determining circuit 406 determines whether the selectioncriterion is fulfilled, and how the selection circuit 304 may select atleast one transmit antenna.

The selection criterion may be based on a receive signal 408 receivedfrom a radio communications network (e.g. a CDMA2000 network, LTEnetwork, etc.) on the plurality of antennas 302 a, 302 b. For example,the selection criterion may be based on a parameter and/or acharacteristic of the receive signal 408. The receive signal 408 may,for example, be received from a network component (e.g. eNB) of theradio communications network on the plurality of antennas 302 a, 302 b.For example, the receive signal 408 may include, or may be, a downlink(DL) signal from the radio communications network (e.g. a CDMA2000network, LTE network, etc.).

The communications terminal 300 may include a receiver 402 configured toreceive the receive signal 408 from the plurality of antennas 302 a, 302b. For example, the receiver 402 may be connected (e.g. electricallyand/or communicatively connected) to the plurality of antennas 302 a,302 b. The connection between the receiver 402 and the plurality ofantennas 302 a, 302 b is indicated as connection 402 a in FIG. 4. Thereceiver 402 may be configured to provide the receive signal 408received from the plurality of antennas 302 a, 302 b to, for example,the determining circuit 406. The provision of the receive signal 408 bythe receiver 402 to the determining circuit 406 may be indicated by thegroup of arrows 402 b shown in FIG. 4.

As described above, the selection criterion may be based on a parameterof the receive signal 408. Use of the parameter of the receive signal408 (e.g. a DL signal) in selecting the transmit antenna may be possibledue to reciprocity of an UL channel and a DL channel (described above inrelation to FIG. 1). For example, a parameter of the receive signal 408may indicate the quality of a DL channel from the radio communicationsnetwork to the plurality of antennas 302 a, 302 b. The quality of an ULchannel in an opposite direction (e.g. from the plurality of antennas302 a, 302 b to the radio communications network) may, for example, beinferred from this parameter.

The plurality of antennas 302 a, 302 b may exhibit parallel reception ofthe receive signal 408 (e.g. DL signal). In other words, the receivesignal 408 (e.g. DL signal) may be received by each antenna of theplurality of antennas 302 a, 302 b, for example, at the same time.Stated in yet another way, the receive signal 408 may be receivedconcurrently by each antenna of the plurality of antennas 302 a, 302 b.Accordingly, a parameter of the receive signal 408 (e.g. DL signal) maybe determined (e.g. by the determining circuit 406) for each antenna ofthe plurality of antennas 302 a, 302 b, and the parameter associatedwith each antenna of the plurality of antennas 302 a, 302 b may be used(e.g. by the selection circuit 304) to infer the quality of an ULchannel from a respective antenna of the plurality of antennas 302 a,302 b to the radio communications network (e.g. a network component ofthe radio communications network).

The parameter of the receive signal 408 may include, or may be, a powerof the receive signal 408 (e.g. DL signal). In this regard, severalmeasures of the power of the receive signal 408 may be available.

The power of the receive signal 408 may include, or may be, a totalpower of the receive signal 408 (e.g. DL signal). For example, thereceive signal 408 (e.g. DL signal) may include an information bearingsignal (e.g. a reference signal), thermal noise, interference (e.g.co-channel and/or inter-channel interference) and possibly othersources. Therefore, the power of each of these components of the receivesignal 304 (e.g. DL signal) may contribute to the total power of thereceive signal 408 (e.g. DL signal). The selection criterion may bebased on the total power of the receive signal. For example, the totalpower of the receive signal 408 received at the plurality of antennas302 a, 302 b (e.g. at each antenna of the plurality of antennas 302 a,302 b) may give an indication of the quality of an UL channel betweeneach antenna of the plurality of antennas 302 a, 302 b and the networkcomponent from which the receive signal 408 is received. For example, ahigh RSSI (Receive Signal Strength Indicator) of a receive signal 408(e.g. DL signal) received in, for example, an IEEE 802.11 radiocommunications system, may indicate a high quality UL channel.Accordingly, the selection circuit 304 may select an antenna of theplurality of antennas 302 a, 302 b with a high (e.g. the highest) RSSIas the transmit antenna. Conversely, if an antenna of the plurality ofantennas 302 a, 302 b is covered by a hand of a user of thecommunications terminal 300, that antenna may have a lower RSSI in theDL channel, and this may, for example, indicate poor channel conditionsin the UL channel. Determination of the total power of the receivesignal 408 by the determining circuit 406 is indicated as “Mechanism A”in FIG. 4.

As described above, the total power of the receive signal 408 mayinclude contributions from an information bearing signal (e.g. referencesignal), thermal noise, interference (e.g. co-channel and/orinter-channel interference) and possibly other sources. Therefore, anantenna receiving a high noise power and a low information bearingsignal (e.g. reference signal) power may have the same total power ofthe receive signal 408 as another antenna receiving a low noise powerand a high information bearing signal (e.g. reference signal) power.This may, for example, be possible when the beam pattern of therespective antennas point in different directions. Accordingly, basingthe selection criterion on the total power of the receive signal 408received on the plurality of antennas 302 a, 302 b (e.g. on each antennaof the plurality of antennas 302 a, 302 b) may not give an accurateindication of the quality of an UL channel. Therefore, another measureof the power of the receive signal 408 may be necessary.

Accordingly, the power of the receive signal 408 may include, or may be,a power of a reference signal (or a signal not considered asinterference and/or noise) included in the receive signal 408. In otherwords, the parameter of the receive signal 408 determined by thedetermining circuit 406 may include, or may be, a power of a referencesignal (or a signal not considered as interference and/or noise)included in the receive signal 408. The selection criterion maytherefore be based on the power of the reference signal included in thereceive signal 408. For example, a RSCP (Receive signal Code Power) ofthe receive signal 408 may be a measure of the power of a referencesignal included in the receive signal 408 (e.g. DL signal, e.g. DLsignal in a UMTS communications system). By way of another example, aRSRP (Reference Signal Received Power) of the receive signal 408 may bea measure of the power of a reference signal included in the receivesignal 408 (e.g. DL signal, e.g. DL signal in a LTE communicationssystem). Accordingly, the selection circuit 304 may select an antenna ofthe plurality of antennas 302 a, 302 b with a high (e.g. the highest)RSRP and/or RSCP as the transmit antenna. Conversely, if an antenna ofthe plurality of antennas 302 a, 302 b is covered by a hand of a user ofthe communications terminal 300, that antenna may have a lower RSRPand/or RSCP in the DL channel, and this may indicate poor channelconditions in the UL channel.

Determination of the power of the reference signal (or a signal notconsidered as interference and/or noise) included in the receive signal408 (e.g. by the determining circuit 406) may be contingent on thereference signal or measurements of the reference signal (e.g. powermeasurements of the reference signal) being available and/or provided tothe communications terminal 300. In this regard, RATs (radio accesstechnologies), such as, for example, LTE, CDMA200, etc., may beconfigured to provide measurements of a reference signal (e.g. powermeasurements of a reference signal) as part of handover decisionsbetween cells of a RAT (e.g. when the communications terminal 300 movesfrom one cell to another). Accordingly, such measurements of the powerof the reference signal may be available in current RATs, and this maybe used to determine the power of the reference signal. Determination ofthe power of the reference signal included in the receive signal 408 bythe determining circuit 406 is indicated as “Mechanism B” in FIG. 4.

As described above, the receive signal 408 may include an informationbearing signal (e.g. reference signal), thermal noise, interference(e.g. co-channel and/or inter-channel interference) and possibly othersources. In other words, the receive signal 408 may include a referencesignal and noise (which may include thermal noise, interference andpossibly other sources other than the reference signal).

Accordingly, the power of the receive signal 408 may include, or may be,a ratio of a power of the reference signal to a power of the noise. Thisratio may also be referred to as a signal-to-noise ratio (SNR) orsignal-to-interference and noise ratio (SINR) of the receive signal 408.In other words, the parameter of the receive signal 408 determined bythe determining circuit 406 may include, or may be, a SNR or SINR of thereceive signal 408. The selection criterion may be based on the SNR orSINR of the receive signal 408. For example, the receive signal 408 maybe received on the plurality of antennas 302 a, 302 b over a commonchannel (e.g. a pilot channel) or a dedicated channel for a user of thecommunications terminal 300. For example, a PDSCH (Physical DownlinkShared Channel) may be used in an LTE communications system, in whichcase the SNR or SINR may include, or may be, a RSRQ (Reference SignalReceived Quality). By way of another example, a DPCH (Dedicated PhysicalChannel) may be used in a 3G communications system, in which case theSNR or SINR may include, or may be, the Ec/Io of the DPCH. Determinationof the SNR or SINR of the receive signal 408 by the determining circuit406 is indicated as “Mechanism C” in FIG. 4.

In summary, the selection criterion may be based on a parameter of thereceive signal 408. The parameter of the receive signal 408 may bedetermined by the determining circuit 406. The parameter of the receivesignal 408 may include, or may be, a power of the receive signal 408.The power of the receive signal 408 may, for example, include, or maybe, at least one of: a total power of the receive signal 408, a power ofa reference signal included in the receive signal 408 and a SNR or SINRof the receive signal 408.

As described above in relation to FIG. 1, in a soft handover system(e.g. in a 3G communications system) there may potentially be more thanone cell serving the communications terminal 300. In other words, thecommunications terminal may receive a plurality of receive signals 408,each receive signal of the plurality of receive signals 408 beingreceived from a respective network component of a radio communicationssystem. In such an example, the determining circuit 406 may determine aparameter for each receive signal of the plurality of receive signals408. Thereafter, the determining circuit 406 may select and/or combinethe parameters determined for the plurality of receive signals 408.

For example, the determining circuit 406 may combine the parameters bysumming the parameters determined for the plurality of receive signals408. By way of another example, the determining circuit 406 may combinethe parameters by taking a weighted sum of the parameters determined forthe plurality of receive signals 408. By way of yet another example, thedetermining circuit 406 may select the a parameter (e.g. best parameter,for example, a highest value) of the plurality of parameters determinedfor the plurality of receive signals 408.

The way the parameters of the plurality of receive signals 408 areselected and/or combined may depend on a reliability factor of thenetwork components from which the plurality of receive signals 408 isreceived. For example, the reliability factor of the network componentsmay include, or may be, an uplink reliability factor.

For example, the uplink reliability factor of the network components maybe indicated by the number of ACKs/NACKs received by the communicationsterminal 300 for an uplink packet sent to the network components. Forexample, the parameter of the receive signal 408 received from thenetwork component which may send the most number of ACKs to thecommunications terminal 300 may be selected by the determining circuit408.

By way of another example, the uplink reliability factor of the networkcomponents may include, or may be, an uplink power control commandreceived from the network components. For example, a network componentwhich sends the most power down commands, may have the best reception inthe uplink from the communications terminal 300 to the networkcomponent. Accordingly, the parameter of the receive signal 408 receivedfrom this network component could be selected. By way of anotherexample, the network components with the most power up requests may betaken into account in a weighting of the parameters of the receivesignal 408 received from the network components.

By way of yet another example, the uplink reliability factor of thenetwork components may include, or may be, an uplink grant. For example,a 3G E-DCH (enhanced dedicated channel) transmission may rely on uplinkgrants from more than just the serving cell. Neighboring cells maydowngrade the grant in order to control uplink interference. Thisinformation may be used to control the antenna selection.

To further increase data throughput, new standards may specify carrieraggregation. In other words, the receive signal 408 may be received onthe plurality of antennas 302 a, 302 b over a plurality of frequenciesand/or frequency bands. The plurality of frequencies and/or frequencybands may include a main carrier and one or more sub-carriers. Forexample, in a 3G communications system, a carrier aggregation may bespecified for a downlink connection, e.g. DC-HSDPA (Dual ChannelHigh-Speed Downlink Packet Access), and/or for an uplink connection,e.g. DC-HSUPA (Dual Channel High-Speed Uplink Packet Access). Thus, theabove-described parameters (e.g. total power, power of reference signal,SNR, SINR) may be determined by the determining circuit 406 for multiplefrequencies or bands (e.g. for each frequency of the plurality offrequencies). In other words, the parameter of the receive signal 408may include a plurality of frequency-specific parameters. Eachfrequency-specific parameter may be, for example, the parameter of thereceive signal 408 received on a respective frequency or frequency bandof the plurality of frequencies. For example, a frequency-specificparameter may include, or may be, a total power of the receive signal408 at a particular frequency (or frequency band) and/or a power of areference signal at a particular frequency (or frequency band) and/or anSNR of the receive signal 408 at a particular frequency (or frequencyband) and/or an SINR of the receive signal 408 at a particular frequency(or frequency band). The selection criterion may be based on at leastone frequency-specific parameter determined by the determining circuit406. For example, the selection criterion may be based on a selection ofat least one frequency-specific parameter and/or a combination of two ormore frequency-specific parameters. For example, a selection and/orcombination criteria may be for the main carrier to take prioritybecause it may contain the most amount of information of the receivesignal 408. By way of another example, a selection and/or combinationcriteria may be to select the frequency-specific parameter of thereceive signal 408 that is received on the carrier that provides thehighest throughput in an uplink and/or downlink. By way of yet anotherexample, a selection and/or combination criteria may be to weight thefrequency-specific parameters based their throughput contribution. Inother words, the selection criterion may be based on at least onefrequency-specific parameter of the plurality of frequency specificparameters. Determination of a parameter of the receive signal 408 for aplurality of frequencies by the determining circuit 406 is indicated as“Mechanism D” in FIG. 4.

As described above, the receive signal 408 (e.g. DL signal) may bereceived by each antenna of the plurality of antennas 302 a, 302 b, forexample, at the same time. In other words, all antennas of the pluralityof antennas 302 a, 302 b may be required to be turned on (e.g. activelyreceiving) during reception of the receive signal 408 (e.g. DL signal).However, this may not always be possible in the communications terminal300. For example, with dynamic receive diversity, at least one antennamay be switched off and at least one antenna may be switched on duringreception of the receive signal 408. This may be done for the receiver402 to save power. Accordingly, in order to determine theabove-described parameters, all antennas of the plurality of antennas302 a, 302 b may need to be switched on in order to receive the receivesignal 408 at the same time. The plurality of antennas 302 a, 302 b maybe switched on for a very short time, and thus may not significantlyimpact the power consumption of the communications terminal 300.

There may, for example, be a receive trigger that may cause all antennasof the plurality of antennas 302 a, 302 b to be switched on for a shorttime in order to receive the receive signal 408 at the same time (e.g.concurrently or simultaneously). This receive trigger may, for example,be for instructing each antenna of the plurality of antennas 302 a, 302b to receive the receive signal 408 from the radio communicationsnetwork at the same time. The determining circuit 406 may be configuredto provide the receive trigger to the plurality of antennas 302 a, 302b. The provision of the receive trigger to the plurality of antennas 302a, 302 b is indicated as arrow 406 b in FIG. 4. As shown in FIG. 4, thereceive trigger may, for example, trigger the connection 402 a with theplurality of antennas 302 a, 302 b, thus enabling the plurality ofantennas 302 a, 302 b to receive the receive signal 408 from the radiocommunications network at the same time (i.e. concurrently orsimultaneously).

The receive trigger may be provided by the determining circuit 406 tothe plurality of antennas 302 a, 302 b regularly or on upon an event.For example, the determining circuit 406 may store (e.g. in memory) theparameter of the receive signal 408 previously determined by it. By wayof another example, the determining circuit 406 may store (e.g. inmemory) a plurality of previously determined parameters of the receivesignal 408. By way of yet another example, the determining circuit 406may store (e.g. in memory) an average of the previously determinedparameters of the receive signal 408. The determining circuit 406 may,for example, determine how recent the parameters of the receive signal408 stored (e.g. in a memory) are. If the parameters (e.g. an average ofa prescribed number of a previously determined parameters) are recent,the determining circuit 406 may not provide the receive trigger to theplurality of antennas 302 a, 302 b. However, if the parameters aredetermined to be old (e.g. because dynamic receiver diversity hasdeactivated one antenna for a long time), e.g., more than 3 seconds,then the determining circuit 406 may provide the receive trigger to theplurality of antennas 302 a, 302 b, for example, to obtain an up-to-datemeasurement of the receive signal 408. This may enable the determiningcircuit 406 to determine an up-to-date parameter of the receive signal408. In summary, the determining circuit 408 may store (e.g. in memory)previously determined parameters of the receive signal 408, and may befurther configured to determine whether the previously determinedparameters of the receive signal are outdated. The determining circuit408 may provide the receive trigger to the plurality of antennas 302 a,302 b if it determines that the previously determined parameters of thereceive signal are outdated. Use of this procedure by the determiningcircuit 406 is indicated as “Mechanism E” in FIG. 4.

As described above, the receive signal 408 may be received on theplurality of antennas 302 a, 302 b from a plurality of networkcomponents (i.e. a plurality of cells). When the selection circuit 304selects a transmit antenna based on parameters of the receive signal 408that may be cell specific, different strategies may be possibleregarding which cell to use. For example, the communications terminal300 may request a handover to another cell (i.e. a target cell) becausethat other cell would be better. In other words, the target cell may bea radio cell specified in a handover request sent by the communicationsterminal 300 to the radio communications network. In such an example,the determining circuit 406 may determine the parameter of the receivesignal 408 received from the target cell and the determining circuit 406may determine in advance the best transmit antenna for the target cell.If this is a different one than on the current cell, the switching tothe selected transmit antenna (e.g. by the selection circuit 304) could,for example, take place at the point of handover. In other words, theselection criterion may be based on a parameter of the receive signal408 received from a cell specified in a handover request sent by thecommunications terminal 300 to the radio communications network. In asoft handover system (e.g. in a 3G communications system), where theremay be an active set with multiple serving cells, the selection circuit304 may add a requested new cell to its decision matrix for the softhandover cells (e.g. see above description) to come to the optimalcondition when the new cell would be added to the active set. In thesame way one could exclude a cell of the active set, which thecommunications terminal 300 may ask the radio communications network toremove from the decision matrix. Use of this procedure by thedetermining circuit 406 is indicated as “Mechanism F” in FIG. 4.

In summary, the preceding examples show that the selection criterion maybe based on, for example, a parameter of the receive signal 408 receivedfrom the radio communications network (e.g. a CDMA2000 network, LTEnetwork, etc.) on the plurality of antennas 302 a, 302 b. Thedescription that follows provides examples which show that the selectioncriterion may be based on control information that may, for example, bereceived from the radio communications network on the plurality ofantennas. The control information may, for example, control atransmission of a transmit signal 508 on the plurality of antennas 302a, 302 b.

The communications terminal 300 may include a transmitter 404 configuredto transmit the transmit signal 508 on at least one antenna of theplurality of antennas 302 a, 302 b. The transmitter 404 may, forexample, control the transmission of the transmit signal 508 based oncontrol information. The control information may be provided to thecommunications terminal 300 by the radio communications network. Forexample, the control information may be known to the transmitter 404based on a communication between the communications terminal 300 and anetwork component of the radio communications network (e.g. with a BSprotocol stack). By way of another example, the control information maybe stored in a protocol stack of the communications terminal 300 (e.g. aUE).

The transmitter 404 may be configured to provide the control informationto the determining circuit 406. In other words, the determining circuit406 may be configured to receive the control information from thetransmitter 404. The provision of the control information by thetransmitter 404 to the determining circuit 406 may be indicated by thegroup of arrows 404 b shown in FIG. 4.

The control information may include, or may be, power controlinformation. The power control information may, for example, be providedto the communications terminal 300 by a network component (e.g. a basestation) of the radio communications network. For example, the networkcomponent may request the communications terminal 300 via the powercontrol information to transmit the transmit signal 508 at a particularpower. In other words, the power control information may be suitable forcontrolling a transmission power of the transmit signal 508 on theplurality of antennas. Stated in yet another way, the power controlinformation may control the power of the transmitter 404 whentransmitting the transmit signal 508.

As described above, the determining circuit 406 may be configured todetermine whether the selection criterion is fulfilled. The determiningcircuit 406 may use the transmission power to verify whether thisdetermination was correct. In other words, the transmission power may beused to verify whether the selected transmit antenna was a correctchoice. For example, the determining circuit 406 may compare thetransmission power on the transmit antenna to the transmission power ona previous transmit antenna (e.g. previously selected transmit antenna),which may be stored in a memory of the determining circuit 406. In otherwords, the determining circuit 406 may be configured to compare thetransmission power of the transmit signal 508 prior to selection of thetransmit antenna (e.g. by the selection circuit 304) and thetransmission power of the transmit signal 508 after selecting thetransmit antenna (e.g. by the selection circuit 304). This procedurecould be used to verify if selection of the transmit antenna wascorrect. If the determining circuit 406 determines that selecting thetransmit antenna was not the correct decision (e.g. if the transmissionpower after selecting the transmit antenna is larger than thetransmission power prior to selecting the transmit antenna), thedetermining circuit 406 may provide a selection trigger to selectioncircuit 304, which may cause the selection circuit 304 to select anotherantenna. In other words, the selection criterion may be based on acomparison of the transmission power of the transmit signal 508 prior toselecting the transmit antenna and the transmission power of thetransmit signal 508 after selecting the transmit antenna.

When determining the transmission power, the determining circuit 406could, for example, average over a certain period of time. A comparisonof a previous and a present transmission power by the determiningcircuit 406 may show that there may be substantially no difference inthe previous and present transmission powers. This may mean that theremay be no significant change in the radio conditions. To cross-check ifthe negligible difference between the previous and present transmissionpowers is indeed due to no significant change in the radio conditions,the determining circuit 406 could check if other values like RSSI, RSRP,RSCP, etc. have changed significantly or not. In other words, theselection circuit 304 may be further configured to reselect at least oneother antenna of the plurality of antennas 304 a, 304 b as a newtransmit antenna in case the transmission power of the transmit signal508 after selecting the transmit antenna is greater than thetransmission power of the transmit signal prior to selecting thetransmit antenna. Determination of a previous and a present transmissionpower by the determining circuit 406 is indicated as “Mechanism I” inFIG. 4.

The control information may include, or may be, radio link control (RLC)information. In other words, the control information may include, or maybe, control information in the radio link control (RLC) communicationlayer. The RLC information may, for example, be known to thecommunications terminal 300 (e.g. stored in a protocol stack of thecommunications terminal 300).

The selection criterion may be based on the RLC information. Forexample, the number of pending ACKs (data received acknowledgements) maybe considered as a measure of transmit quality on an RLC level in, forexample, an RLC Acknowledged mode. Accordingly, the number of pendingACKs may be considered a measure of the likelihood that the transmitsignal 508 is received by the radio communications system. For example,the communications terminal 300 may send the transmit signal 508 on aDCCH (Dedicated Control Channel), e.g. a UL DCCH. The transmit signal508 may, for example, be an event based measurement report such as a 3Gevent 2 f, which may be used to deactivate a CM (configuration manager)of the radio communications network (e.g. event 1 b). The transmitsignal 508 (e.g. sent on UL DCCH) may not be received by the radiocommunications network or the radio communications network may not beable to demodulate the transmit signal 508. Accordingly, the number ofpending ACKs on the side of the communications terminal 300 may increase(e.g. incremented). Accordingly, a high number of pending ACKs mayindicate to the selection circuit 304 that the currently used transmitantenna may not be successfully transmitting the transmit signal 508. Atthe same time the number of “Request for Retransmissions” from the radiocommunications network side may increase, despite attempts by thecommunications terminal 300 to retransmit the transmit signal 508. Thismay proceed until, for example, the RLC of the communications terminal300 hits a “max retransmission counter” indicating that the maximumnumber of retransmission attempts has been reached by the communicationsterminal 300. This may trigger an RLC reset in the communicationsterminal 300, which may result in a RLF (Radio link failure). Thisscenario would indicate to the determining circuit 406 on an RLC levelthat the currently used transmit antenna may not successfullytransmitting the transmit signal 508 to the network. Accordingly, thedetermining circuit 406 may consequently provide the selection triggerto the selection circuit 304, which may select a new transmit antenna.Provision of control information in the RLC communication layer to thedetermining circuit 406 is indicated as “Mechanism P” in FIG. 4.

The control information may include, or may be, control information in aradio resource control (RRC) communication layer. The controlinformation in the RRC communication layer may, for example, indicate achange in an uplink channel condition, which may require selection of anew transmit antenna. For example, control information in the RRCcommunications layer may include, or may be, CQI (Channel QualityInformation) reporting configuration settings. For example, CQI may besent to the radio communications network, e.g. by the communicationsterminal 300. In other words, CQI may be reported to the radiocommunications network (e.g. by the communications terminal 300). Theradio communications network may, for example, control the frequencywith which the CQI is reported (e.g. by the communications terminal 300)by means of CQI reporting configuration settings, which may be sent aspart of, or as, control information in the RRC communications layer. Thefrequency with which the CQI has to be reported to the radiocommunications network (e.g. by the communications terminal 300) may,for example, indicate a change in an uplink channel condition, which mayrequire selection of a new transmit antenna.

For example, during HSDPA (High Speed DL Packet Access) operation (e.g.in the case of PS-only (packet switched) or MRAB (multiple radio accessbearers)), CQI is transmitted on the HS-DPCCH (High Speed DedicatedPhysical Control Channel). The following parameters may characterize thefrequency with which the CQI information is reported to the network. Thefirst of these parameters may be CQI Feedback Cycle. This parameter mayset a CQI feedback cycle value signaled to the communications terminal300, which may control how often the communications terminal 300transmits new CQI information on the uplink. A value of zero means thatthe communications terminal 300 does not transmit any CQI information.When CQI Feedback Cycle is not zero, it may be greater than or equal to(CQI Repetition Factor*2 ms). The second of these parameters may be CQIRepetition Factor. This parameter may set a CQI repetition factorsignalled to the communications terminal 300, which may control howoften the communications terminal 300 repeats CQI information on theuplink. In case of degraded UL, the CQI information does not reach theradio communications network. In order to increase the probability thatthe radio communications network receives CQI information, the radiocommunications network might react with decreasing the CQI FeedbackCycle or increasing the CQI Repetition Factor i.e. initiating in thecommunications terminal 300 to send CQI information more often. Thischange in the communications terminal 300 may be signaled via a RadioBearer Reconfiguration on RRC (Radio Resource Control) level. Change ofone of these, or both, values may be evaluated and interpreted by thedetermining circuit 406 as degraded UL conditions, and the determiningcircuit 406 may consequently provide the selection trigger to theselection circuit 304 to switch the transmit antenna. Provision ofcontrol information in the radio resource control (RRC) communicationlayer to the determining circuit 406 is indicated as “Mechanism Q” inFIG. 4.

The control information may include, or may be, control information forcontrolling an uplink data transmission parameter of the transmission ofthe transmit signal 508. For example, UL data transmission parametersmay include grants (e.g. scheduling grants) and/or average ACK/NACKs.For example, in a HSUPA (High-Speed Uplink Packet Access) in a 3Gcommunications network or in a PUSCH (Physical Uplink Shared Channel) inan LTE communications channel, a network component (e.g. NB) may providethe communications terminal 300 with a certain grant, which may includehow much data the communications terminal 300 may transmit (e.g. bymeans of how often the communications terminal 300 may transmit,indicated by scheduling grants) and e.g. which modulation and codingscheme (MCS) may be used. Therefore, these grants may provide anindicator for the uplink link quality. The grants may also be impactedby other parameters like network load, e.g. resources available at thenetwork component (e.g. NB) or the uplink multiple access scheme ingeneral. The determining circuit 406 may determine the grant achievedfor each antenna of the plurality of antennas 302 a, 302 b, and may usethis to determine if the selection criterion is fulfilled. The selectioncircuit 304 may select the antenna which provides the better uplinkgrant, and may switch the antenna test-wise to evaluate the otherantenna (see description below in respect of Mechanism K). In additionto the grant, the determining circuit 406 may also determine the averageACK/NACKs the communications terminal 300 receives for transmission ofthe transmit signal 508 on the different antennas. The ACK/NACKs alsoprovide an indicator for the uplink quality and can be, for example, becombined with the grant. The grant may provide only an estimate of theuplink quality by the network component (e.g. NB), while the ACK/NACKsmay give an indicator on the success of the uplink transmissions. Thus,average ACK/NACKs per antenna could also be used as a parameter by theselection circuit 304 to select the best transmit antenna. Provision ofcontrol information for controlling the UL data transmission parametersto the determining circuit 406 is indicated as “Mechanism R” in FIG. 4.

The communications terminal 300 may include at least one antenna tuningcircuit 510 which may be configured to provide a feedback signal fromthe plurality of antennas 302 a, 302 b. The at least one antenna tuningcircuit 510 may, for example, be used to detect whether an antenna ofthe plurality of antennas 302 a, 302 b is detuned, and may be furtherconfigured to re-tune a detuned antenna upon detection of such a detunedantenna. For example, objects, such as the user's hand or head, in thenear field of an antenna can detune the antenna. Therefore, antennas maybe equipped with an automatic tuning mechanism (e.g. an adaptivematching network), for example by means of the at least one antennatuning circuit 510 that may aim at re-tuning the antenna. A feedbacksignal 512 from the plurality of antennas 302 a, 302 b, sent through theat least one antenna tuning circuit 510, could be used to identify adetuned antenna. The determining circuit 406 may determine a parameterof the feedback signal 512, and this parameter may be used to determineif the selection criterion is fulfilled. The parameter of the feedbacksignal 512 may include, or may be, an indication of a degree of detuningof an antenna of the plurality of antennas 302 a, 302 b. In other words,the determining circuit 406 may determine a degree of detuning of anantenna of the plurality of antennas 302 a, 302 b, and the degree ofdetuning of the antenna may be used to determine if the selectioncriterion is fulfilled. Assuming that the automatic tuning mechanism isnot able to fully correct the detuning, the selection circuit 304 mayavoid selecting a detuned antennas as the transmit antenna, or theleast-detuned antenna could be selected as the transmit antenna.Provision of the feedback signal 512 to the determining circuit 406 isindicated as “Mechanism S” in FIG. 4.

In summary, the preceding examples show that the selection criterion maybe based on control information that may, for example, be received fromthe radio communications network on the plurality of antennas 302 a, 302b and/or on a feedback signal 512 received from the plurality ofantennas 302 a, 302 b via, for example, at least one antenna tuningcircuit 510. The description that follows provides examples which showhow the determining circuit 406 may determine whether the selectioncriterion is fulfilled, and how the selection circuit 304 may select thetransmit antenna based on the selection criterion.

As described above, the determining circuit 406 may compare values (e.g.a first value with at least one other value) to, for example, determineif the selection criterion is fulfilled and to consequently determinethe best antenna to use as a transmit antenna. When comparing values(e.g. an antenna specific RSSI), an antenna whose value indicates abetter channel quality (e.g. antenna with the higher RSSI) may always beselected as the transmit antenna. However, if the values for theantennas being compared are at least substantially equal (e.g.approximately identical), this could lead to a very frequent switchingbetween or among the antennas being compared. This could have a negativeimpact on the link stability, for example, because the NodeB may seeswitching channel profiles. Therefore, in determining whether theselection criterion is satisfied or fulfilled, the determining circuit406 may apply a threshold. For example the RSSI of a non-active antennamay differ from the RSSI of an active transmit antenna by at least thethreshold before the non-active antenna is selected as the transmitantenna. In other words, the determining circuit 406 may be furtherconfigured to compare a value (e.g. value of a parameter of the receivesignal 408) corresponding an antenna of the plurality of antennas 302 a,302 b with the value (e.g. value of a parameter of the receive signal408) corresponding to at least one other antenna of the plurality ofantennas 302 a, 302 b. The selection criterion may be determined to befulfilled if the values differ by at least a threshold. The thresholdcould be constant or depend on one or more other parameters.

FIG. 5 shows various examples that illustrate a dependency of thethreshold on a magnitude of the value being considered.

The threshold may show no dependency on the magnitude of the value (e.g.in 600). The threshold may show a linear dependency on the magnitude ofthe value (e.g. in 602). The threshold may show a step dependency on themagnitude of the value (e.g. in 604). Other types of relationshipsbetween the threshold and the magnitude of the parameter may be possible(e.g. table look-up or any other kind of relationship or a combination,e.g. step-wise with linear dependency).

For example, the threshold may depend on a magnitude (e.g. absolutevalue) of the value. For example, in graph 602 of FIG. 5, the thresholdcould be larger for values with a high magnitude (e.g. a high RSSI) thanfor values with a low magnitude (e.g. a low RSSI). A high value (e.g. ahigh RSSI) may indicate that the channel conditions are most likelygood, so that a transmit antenna switching is probably not needed.

By way of another example, the threshold may depend on, e.g., thecurrently requested transmit power as indicated by a power controlmechanism (e.g. explicit closed-loop power control signaling from aNodeB). If the requested transmit power is high, the conditions in theUL may not be good, so it may be important to be on the better transmitantenna. Therefore, in this example, the threshold could be small toswitch fast to the potentially better transmit antenna. While for a lowtransmit power, e.g. in good channel conditions, it may not be thatcritical. Thus, a slower switching would be acceptable and safe. A fastswitching at high transmit power could also be advantageous for thepower consumption. For example, a high transmit power may be asignificant contribution to the overall power consumption of thecommunications terminal 300. Thus, when switching fast to a bettertransmit antenna, which requires less transmit power, one could save ameasurable amount of power. For low transmit power the contribution ofthe transmit power to the overall power consumption is only small, sothe potential reduction in power consumption is also only small. The useof a non-constant threshold by the determining circuit 406 to triggerselection of a transmit antenna is indicated as “Mechanism G” in FIG. 4.

The selection of the better transmit antenna (and then switching) could,e.g., take place when the requested transmit power reaches a certainlevel below the maximum transmit power. Accordingly, the threshold mayinclude, or may be, a transmit power lower than the maximum transmitpower. When the requested transmit power reaches this threshold, thismay imply a bad situation or high demand (i.e. high UL throughput).Accordingly, there may be a need to conserve power by switching to abetter transmit antenna may be beneficial. As described above, thevalues determined in the mechanisms described may give an indicationwhich antenna might be a better transmit antenna. However, these areonly predictions and the real performance of the transmit antenna isonly known after switching to the antenna. Switching antennas when, forexample, a requested transmit power of a current transmit antenna isgreater than or equal to the above-described threshold leaves some headroom in case the new transmit antenna is worse. Then one could switchback to the previous transmit antenna if one detects that the transmitpower with the new transmit antenna is actually higher than on theprevious transmit antenna. The use of a threshold including a transmitpower lower than the maximum transmit power by the determining circuit406 to trigger selection of a transmit antenna is indicated as“Mechanism H” in FIG. 4.

As described above in relation to Mechanism I, there may be a chancewhen a power consumed by a selected transmit antenna is actually worsethan a previous transmit antenna. Therefore, one might limit theswitching to non-critical scenarios, for example, where a worseperformance on the new transmit antenna could be corrected by switchingback to the previous transmit antenna without any severe impact on thesystem. Every transmit antenna switching may result in a short glitch ofthe transmitted signal. This may raise the potential need for an antennatuning mechanism for the antennas, and a switched channelprofile/estimation at the NodeB. To avoid any impact on importanttransmissions, the selection of the transmit antenna during transmissionof important messages, e.g. control message (e.g. RLC retransmission) orother critical data may be blocked. In this regard, the communicationsterminal 300 may include a controller 514 configured to determine if acontrol message is exchanged between the plurality of antennas and theradio communications network. The controller 514 may be configured toprovide the selection circuit 304 a block instruction 516 in case itdetermines that a control message is exchanged, the block instruction516 for blocking a reselection of the transmit antenna. The provision ofthe block instruction 516 from the controller 514 to the selectioncircuit 304 is indicated as “Mechanism J” in FIG. 4.

The selection circuit 304 may select a new transmit antenna in regularintervals to check if the other antenna may be a better transmitantenna. In such an example, the determining circuit 406 may determinethe transmit power requested of the new transmit antenna (e.g. after ashort settling period), and in case the new transmit antenna is worse,the selection circuit 304 may switch back to a previous transmitantenna. If however, the new transmit antenna is better, switching maynot be performed, and the determining circuit 406 may determine if aswitch to another antenna is necessary after a time interval. The timeinterval may be depend on another parameter, e.g., in good channelconditions the time interval may be longer than in bad channelconditions. This procedure is indicated as “Mechanism K” in FIG. 4.

A decision to select and/or switch a transmit antenna may also depend onthe state of the communications terminal 300. This could be a generalstate such as idle mode or connected mode. Or it could be a moredetailed state like a HSUPA bearer established in 3G or a highthroughput uplink bearer with LTE. A detailed state may also be usagescenario related, e.g., if a file upload (or download) is ongoing, ahigh or low rate streaming ongoing or some browsing/push mode. Dependingon this, the selection circuit 304 could adapt, e.g., the time intervalsof mechanism K or the thresholds described in mechanism G. The blockingof transmit antenna switching in mechanism J could also depend on thestate, i.e., in certain states the blocking is done and in others not.This procedure is indicated as “Mechanism L” in FIG. 4.

So far it is assumed that the transmit antenna is selected independentlyof the active receive antennas. There may, however, be antennas that maybe operated in duplex mode (i.e. transmit and receive simultaneously).There may be certain effects (positive or negative) if the receive isactive as well on the transmit antenna. For example, there could be asmall cross talk or there might be a small potential on reducing powerconsumption. Accordingly, the selection circuit 304 may take also intoaccount which antenna is actively receiving, e.g., by applying a certainbias in the desired directions to the other mechanisms. This could betaken into account by the selection circuit 304 in selecting a transmitantenna. This procedure is indicated as “Mechanism M” in FIG. 4.

There may also be at least one external parameter, which could influencethe selection of the transmit antenna. An external parameter may referto a parameter (e.g. a measurement or another value), which may not beprovided/obtained by the RAT. For example, an external parameter couldinclude an indication from a sensor of the communications terminal 300,which may detect (e.g. by means of proximity sensors) whether ahand/head/body of a user covers the communications terminal 300. Anotherexternal parameter may be a detection of whether external components areconnected like USB, charger, headset, as these could also affect(usually degrade) antennas close to such connectors. An externalparameter may include information of other RATs which also performmeasurements, e.g., WIFI, Bluetooth or another cellular RAT which ismeasured for an InterRAT handover. An external parameter could include ageneral bias for a certain antenna, which may be a result of the designof the communications terminal 300 or of the plurality of antennas 302a, 302 b of the communications terminal 300. The external parameter maybe provided to the communications terminal 300 by an applicationprocessor and/or another processor and/or a controlling circuit (e.g.WiFi/Bluetooth, or info about the types of antennas built into thecommunications terminal 300). This procedure is indicated as “MechanismN” in FIG. 4.

In FDD deployments, uplink and downlink transmissions may occur atdifferent carrier frequencies which leads to non-identical channelrealizations in downlink and uplink because the fading may depend onwavelength. In TDD deployments, in contrast, downlink and uplinktransmissions are separated in time using the same frequency spectrum.In this case, the uplink and downlink channels can be regarded asperfectly reciprocal meaning that, e.g., the user perceives the samepropagation channel from, for example, eNB antenna A to antenna 302 a ofthe communications terminal 300 as the eNB perceives from antenna 302 ato eNB antenna A. In case of TDD operation, the performance of thereceive antennas measured in the downlink by means ofRSSI/RSRP/RSRQ/SINR/channel matrix/etc. measurements as described aboveand below, can be applied with much higher confidence for the Tx antennaselection mechanism. As the transceiver chains in DL and UL at thecommunications terminal 300 and eNB might be different, even in TDD itmight still be reasonable to aggregate multiple indicators. Thisprocedure is indicated as “Mechanism T” in FIG. 4.

In the description that follows, the selection of more than one antennaas the transmit antenna is described.

Advanced wireless standards may have uplink transmission schemes whichuse more than one antenna, e.g., uplink 2×2 MIMO (multiple-inputmultiple-output) or uplink transmit diversity. Such devices could alsohave more than two receive antennas, e.g., for 4×4 MIMO downlinktransmission or 3 receive antennas to increase downlink diversity. Insuch cases, the mechanisms presented above could be extended to selectthe two best transmit antennas out of, for example, the 4 availablephysical antennas. In general, this means that the mechanisms proposedabove shall not be limited to certain number of transmit antennas orphysical antennas. Special consideration may be given to closed loopuplink MIMO systems, since an applied precoding in the uplink depends onthe uplink channel estimate at the base station receiver. Hence, theswitching can consider relevant feedback timing loop constants. It maybe possible to have interleaved antenna selections. For example, if theuplink precoding at transmission time interval n depends on the uplinkchannel estimation at uplink transmission time interval n−k, then kdifferent selections may be interleaved. These transmission gaps may beused to switch selections. This procedure is indicated as “Mechanism O”in FIG. 4.

For operation with multiple receive antennas in the downlink, acommunications terminal 300 operating in an LTE communications networkmay estimate the SIMO (Single-input multiple-output) or MIMO channelmatrix based on the cell-specific reference symbols (CRS) or channelstate information reference symbols (CSI-RS). Depending on the LTEtransmission mode, the channel matrix may be used for determining thechannel rank for rank indicator (RI) feedback and/or determining theprecoding matrix indicator (PMI) feedback, and/or for MIMO equalizationin, e.g. an MRC (maximum ratio combining) or MMSE (minimum means squareerror) receiver. In addition, the estimated channel matrix can also beused as an input for the transmit antenna selection. By applying asuitable operation like, e.g., a Frobenius norm on the rows of thechannel matrix (assuming a receive-by-transmit layout of the channelmatrix) and, potentially, using a time-averaging mechanism, theantenna(s) with the highest and lowest DL channel gain can be identifiedand the result can be considered for transmit antenna selection. Thisprocedure is indicated as “Mechanism U” in FIG. 4.

Since Release 8 of the LTE standard, closed-loop transmit antennaselection from 2 possible transmit antennas may be an optionalcapability of the communications terminal 300, and this may beconfigured by the eNB. If closed-loop transmit antenna selection isenabled, the communications terminal 300 may alternate between the twoantennas (called A and B here) for the transmission of uplink soundingreference symbols (SRS). Based on the measured UL SRS transmissionquality of antenna A and B, the eNB selects antenna A and B forsubsequent UL transmission and informs the communications terminal 300by appropriately coding the uplink scheduling grant. This closed-loopantenna selection mechanism can be used to select the best N out of Mtransmit antennas (with N=1 out of M>2 being a special case for LTERe1-8 and Re1-9 operation). In multiple phases the communicationsterminal 300 may select 2 out of the M transmit antennas per phase forSRS transmission. After a certain time period during which the eNB hasmeasured the received quality in the communications terminal 300, aranking between the 2 antennas of the currently chosen pair may besignaled in the uplink scheduling grants to the communications terminal300 (potentially averaging over multiple grants). Using the ranking of acandidate transmit antenna pair as an ordering operator, an arbitrarysorting algorithm can be applied to identify the best N transmitantennas out of the total M available transmit antennas. An effect ofexploiting the closed-loop transmit antenna selection feedback is thatthe transmit antenna selection is based on the actually perceivedreceive quality at the eNB. This procedure is indicated as “Mechanism V”in FIG. 4.

In LTE Release 10 and beyond, the communications terminal 300 canutilize multiple transmit antennas to transmit between 1 and 4 spatiallayers by using a precoding matrix, which may be chosen from apre-defined codebook by the eNodeB and signaled to the communicationsterminal 300 in the uplink scheduling grant. To facilitate the channelestimation at the eNB that allows to select the appropriate precodingmatrix, the eNB requests uplink transmissions of antenna-specificsounding reference symbols (SRS) from the communications terminal 300.For the SRS transmission and for the layer-to-antenna mapping during theprecoding operation, an antenna may be identified by its (logical)antenna port number (e.g., ports 20 and 21 for two available transmitantennas and ports 40, 41, 42, and 43 for four available transmitantennas). In a situation where the communications terminal 300 isequipped with more physical antennas than transmit chains or in caseswhere some of the transmit chains should be deactivated, a suitablesubset of N<M transmit antennas from the total M available antennas maybe selected. One way to select these N antennas, may be to alter themapping of the logical antenna ports to the actual physical antennas forSRS transmission and then evaluate the closed-loop precoding feedbackfrom the eNB. For example, for nearly ⅓ of all the rank-1 precodingmatrices that could be selected by the eNB, the precoding matrices maycontain zeros for certain antenna ports, i.e., the eNB indicates todisable a certain antenna port number. By alternating the mapping of Nantenna ports to the M physical antennas and by gathering statisticsover time, the communications terminal 300 may obtain an indicationwhich physical antennas are seen as least suitable by the eNB. Thisprocedure is indicated as “Mechanism W” in FIG. 4.

Whilst the various mechanisms may have been described separately, thecommunications terminal 300 may use two or more mechanisms (e.g. two,three, four, or more mechanisms (e.g. all mechanisms)) jointly in orderto select the transmit antenna for the transmission to the radiocommunications network.

FIG. 6 shows a method 700 for selecting a transmit antenna for atransmission to a radio communications network. The method 700 may, forexample, include: determining whether a selection criterion is fulfilled(in 702); and selecting at least one antenna of the plurality ofantennas as the transmit antenna in case the selection criterion isdetermined to be fulfilled (in 704).

According to various examples described herein, a communicationsterminal may be provided. The communications terminal may include: aplurality of antennas; and a selection circuit configured to select atleast one antenna of the plurality of antennas as a transmit antenna fora transmission to a radio communications network, wherein a selection ofthe transmit antenna may be based on a selection criterion.

The selection criterion may be based on a parameter of a receive signalreceived from the radio communications network on the plurality ofantennas.

The parameter of the receive signal may include a power of the receivesignal.

The power of the receive signal may include a total power of the receivesignal.

The receive signal may include a reference signal, and the parameter ofthe receive signal may include a power of the reference signal.

The receive signal may include a reference signal and noise, and theparameter of the receive signal may include a ratio of a power of thereference signal to a power of the noise.

The receive signal may be received on the plurality of antennas over aplurality of frequencies, the parameter of the receive signal mayinclude a plurality of frequency-specific parameters, eachfrequency-specific parameter of the plurality of frequency-specificparameters may be the parameter of the receive signal received on arespective frequency or frequency band of the plurality of frequencies,and the selection criterion may be based on at least onefrequency-specific parameter.

The plurality of antennas may be configured to receive a receivetrigger, the receive trigger for triggering each antenna of theplurality of antennas to receive the receive signal at the same time.

The plurality of antennas may be configured to receive the receivetrigger in case previously determined parameters of the receive signalare determined to be outdated.

The selection criterion may be based on the parameter of the receivesignal received from a radio cell of the radio communications network,wherein the radio cell may be a cell specified in a handover requestsent by the communications terminal to the radio communications network.

The selection criterion may be based on control information receivedfrom the radio communications network on the plurality of antennas, thecontrol information for controlling a transmission of a transmit signalon the plurality of antennas.

The control information may include power control information, the powercontrol information for controlling a transmission power of the transmitsignal on the plurality of antennas.

The selection criterion may be based on a comparison of the transmissionpower of the transmit signal prior to selecting the transmit antenna andthe transmission power of the transmit signal after selecting thetransmit antenna.

The selection circuit may be further configured to reselect at least oneantenna of the plurality of antennas as a new transmit antenna in casethe transmission power of the transmit signal after selecting thetransmit antenna is greater than the transmission power of the transmitsignal prior to selecting the transmit antenna.

The control information may include control information in a radio linkcontrol (RLC) communication layer.

The control information may include control information in a radioresource control (RRC) communication layer.

The control information in the radio resource control (RRC)communication layer may include channel quality information (CQI)reporting configuration settings.

The channel quality information (CQI) reporting configuration settingsmay include a frequency with which the channel quality information (CQI)is reported to the radio communications network.

The control information may be for controlling an uplink datatransmission parameter of the transmission of the transmit signal on theplurality of antennas.

The uplink data transmission parameter may include a scheduling grant.

The selection criterion may be based on a parameter of a feedback signalreceived from the plurality of antennas.

The feedback signal may include an antenna detuning feedback signal.

The parameter of the feedback signal may include a degree of detuning ofan antenna of the plurality of antennas.

The feedback signal may be received from the plurality of antennas viaan antenna tuning circuit.

The communications terminal may further include the antenna tuningcircuit.

The selection criterion may be determined to be fulfilled in case adifference between a first value and at least one other value is greaterthan or equal to a threshold.

The first value and the at least one other value may include a value ofa parameter of a receive signal received from the radio communicationsnetwork on the plurality of antennas.

The first value and the at least one other value may include a value ofcontrol information for controlling a transmission of a transmit signalon the plurality of antennas.

The first value and the at least one other value may include a value ofa parameter of a feedback signal received from the plurality ofantennas.

The threshold may depend on a magnitude of the first value or the atleast one other value or the first value and the at least one othervalue.

The threshold may depend on a maximum transmit power of the plurality ofantennas.

The communications terminal may further include: a controller configuredto provide a block instruction to the selection circuit, the blockinstruction for blocking the reselection of the transmit antenna by theselection circuit.

The controller may be configured to provide the block instruction to theselection circuit in case a control message is transmitted via theplurality of antennas.

The selection circuit may be configured to select the at least oneantenna of the plurality of antennas as the transmit antenna at regularintervals of time.

The controller may be configured to provide the block instruction to theselection circuit based on a state of the communications terminal.

The selection of the transmit antenna may be based on the selectioncriterion and on information indicating which antenna of the pluralityof antennas is receiving.

The selection criterion may be based on an external parameter determinedby the communications terminal by a means other than a radio accesstechnology.

The external parameter may be determined by at least one of anapplication processor and a controlling circuit, which may be includedin the communications terminal.

The external parameter may include an indication of whether an antennaof the plurality of antennas is covered by an object.

The indication may be provided by a proximity sensor.

The external parameter may be an indication of whether a device isconnected to the communications terminal.

The device may include at least one of a universal serial bus (USB)device, a headset and a charger.

The external parameter may include information of a radio accesstechnology.

The external parameter may include an indication of which antenna of theplurality of antennas is preferred as the transmit antenna.

The selection circuit may be configured to select at least two antennasof the plurality of antennas as transmit antennas for the transmissionto the radio communications network.

The selection of the transmit antennas may be based on an estimateddownlink channel matrix.

The selection of the transmit antennas may be based on a closed-looptransmit antenna selection feedback from the radio communicationsnetwork.

The selection of the transmit antennas may be based on a closed-loopprecoding feedback from the radio communications network.

According to various examples described herein, a method for selecting atransmit antenna for a transmission to a radio communications networkmay be provided. The method may include: determining whether a selectioncriterion is fulfilled; and selecting at least one antenna of theplurality of antennas as the transmit antenna in case the selectioncriterion is determined to be fulfilled.

Determining whether the selection criterion is fulfilled may include:comparing a value of a first signal with a value of a at least one othersignal, and the selection criterion may be determined to be fulfilledbased on the comparison.

Various examples and aspects described in the context of one of thedevices or methods described herein may be analogously valid for theother devices or methods described herein.

While various aspects have been particularly shown and described withreference to these aspects of this disclosure, it should be understoodby those skilled in the art that various changes in form and detail maybe made therein without departing from the spirit and scope of thedisclosure as defined by the appended claims. The scope of thedisclosure is thus indicated by the appended claims and all changeswhich come within the meaning and range of equivalency of the claims aretherefore intended to be embraced.

1. A communications terminal, comprising: a plurality of antennas; and aselection circuit configured to select at least one antenna of theplurality of antennas as a transmit antenna for a transmission to aradio communications network, wherein a selection of the transmitantenna is based on a selection criterion, wherein the communicationterminal receives control information, for controlling a transmission ofa transmit signal via the plurality of antennas, from the radiocommunications network, wherein the control information comprises powercontrol information for controlling a transmission power of the transmitsignal via the plurality of antennas; a determining circuit, based onthe control information, configured to compare the transmission power ofthe transmit signal before selecting the at least one antenna to atransmission power of the transmit signal after selecting the at leastone antenna, and wherein the selection circuit is further configured toreselect at least one antenna of the plurality of antennas as thetransmit antenna if the transmission power of the transmit signal afterselecting the at least one antenna is greater than the transmissionpower of the transmit signal before selecting the at least one transmitantenna.
 2. The communications terminal of claim 1, wherein theselection criterion is based on a parameter of a receive signal receivedfrom the radio communications network on the plurality of antennas. 3.The communications terminal of claim 2, wherein the parameter of thereceive signal comprises a power of the receive signal.
 4. Thecommunications terminal of claim 3, wherein the power of the receivesignal comprises a total power of the receive signal.
 5. Thecommunications terminal of claim 2, wherein the receive signal comprisesa reference signal, and wherein the parameter of the receive signalcomprises a power of the reference signal.
 6. The communicationsterminal of claim 2, wherein the receive signal comprises a referencesignal and noise, and wherein the parameter of the receive signalcomprises a ratio of a power of the reference signal to a power of thenoise.
 7. The communications terminal of claim 2, wherein the receivesignal is received on the plurality of antennas over a plurality offrequencies, wherein the parameter of the receive signal comprises aplurality of frequency-specific parameters, wherein eachfrequency-specific parameter of the plurality of frequency-specificparameters is the parameter of the receive signal received on arespective frequency or frequency band of the plurality of frequencies,and wherein the selection criterion is based on at least onefrequency-specific parameter.
 8. The communications terminal of claim 2,wherein the plurality of antennas is configured to receive a receivetrigger, the receive trigger for triggering each antenna of theplurality of antennas to receive the receive signal at the same time. 9.The communications terminal of claim 8, wherein the plurality ofantennas is configured to receive the receive trigger in case previouslydetermined parameters of the receive signal are determined to beoutdated.
 10. The communications terminal of claim 2, wherein theselection criterion is based on the parameter of the receive signalreceived from a radio cell of the radio communications network, whereinthe radio cell is a cell specified in a handover request sent by thecommunications terminal to the radio communications net wk. 11-14.(canceled)
 15. The communications terminal of claim 11, wherein thecontrol information comprises control information in a radio linkcontrol (RLC) communication layer.
 16. The communications terminal ofclaim 11, wherein the control information comprises control informationin a radio resource control (RRC) communication layer.
 17. Thecommunications terminal of claim 16, wherein the control information inthe radio resource control (RRC) communication layer comprises channelquality information (CQI) reporting configuration settings.
 18. Thecommunications terminal of claim 17, wherein the channel qualityinformation (CQI) reporting configuration settings comprises a frequencywith which the channel quality information (CQI) is reported to theradio communications network.
 19. The communications terminal of claim11, the control information for controlling an uplink data transmissionparameter of the transmission of the transmit signal on the plurality ofantennas.
 20. The communications terminal of claim 19, wherein theuplink data transmission parameter comprises a scheduling grant.
 21. Thecommunications terminal of claim 1, wherein the selection criterion isbased on a parameter of a feedback signal received from the plurality ofantennas.
 22. The communications terminal of claim 21, wherein thefeedback signal comprises an antenna detuning feedback signal.
 23. Thecommunications terminal of claim 22, wherein the parameter of thefeedback signal comprises a degree of detuning of an antenna of theplurality of antennas.
 24. The communications terminal of claim 21,wherein the feedback signal is received from the plurality of antennasvia an antenna tuning circuit.
 25. (canceled)
 26. The communicationsterminal of claim 1, wherein the selection criterion is determined to befulfilled in case a difference between a first value and at least oneother value is greater than or equal to a threshold.
 27. Thecommunications terminal of claim 26, wherein the first value and the atleast one other value comprise a value of a parameter of a receivesignal received from the radio communications network on the pluralityof antennas.
 28. The communications terminal of claim 26, wherein thefirst value and the at least one other value comprise a value of controlinformation for controlling a transmission of a transmit signal on theplurality of antennas.
 29. The communications terminal of claim 26,wherein the first value and the at least one other value comprise avalue of a parameter of a feedback signal received from the plurality ofantennas.
 30. The communications terminal of claim 26, wherein thethreshold depends on a magnitude of the first value or the at least oneother value or the first value and the at least one other value.
 31. Thecommunications terminal of claim 26, wherein the threshold depends on amaximum transmit power of the plurality of antennas.
 32. Thecommunications terminal of claim 1, further comprising: a controllerconfigured to provide a block instruction to the selection circuit, theblock instruction for blocking the reselection of the transmit antennaby the selection circuit.
 33. The communications terminal of claim 32,wherein the controller is configured to provide the block instruction tothe selection circuit in case a control message is transmitted via theplurality of antennas.
 34. The communications terminal of claim 1,wherein the selection circuit is configured to select the at least oneantenna of the plurality of antennas as the transmit antenna at regularintervals of time.
 35. The communications terminal of claim 32, whereinthe controller is configured to provide the block instruction to theselection circuit based on a state of the communications terminal. 36.The communications terminal of claim 1, wherein the selection of thetransmit antenna is based on the selection criterion and on informationindicating which antenna of the plurality of antennas is receiving. 37.The communications terminal of claim 1, wherein the selection criterionis based on an external parameter determined by the communicationsterminal by a means other than a radio access technology.
 38. Thecommunications terminal of claim 37, wherein the communications terminalcomprises at least one of an application processor and a controllingcircuit, and wherein the external parameter is determined by at leastone of the application processor and the controlling circuit.
 39. Thecommunications terminal of claim 37, wherein the external parametercomprises an indication of whether an antenna of the plurality ofantennas is covered by an object.
 40. The communications terminal ofclaim 39, wherein the indication is provided by a proximity sensor. 41.The communications terminal of claim 37, wherein the external parametercomprises an indication of whether a device is connected to thecommunications terminal.
 42. The communications terminal of claim 41,wherein the device comprises at least one of a universal serial bus(USB) device, a headset and a charger.
 43. The communications terminalof claim 37, wherein the external parameter comprises information of aradio access technology.
 44. The communications terminal of claim 37,wherein the external parameter comprises an indication of which antennaof the plurality of antennas is preferred as the transmit antenna. 45.The communications terminal of claim 1, wherein the selection circuit isconfigured to select at least two antennas of the plurality of antennasas transmit antennas for the transmission to the radio communicationsnetwork.
 46. The communications terminal of claim 45, wherein theselection of the transmit antennas is based on an estimated downlinkchannel matrix.
 47. The communications terminal of claim 45, wherein theselection of the transmit antennas is based on a closed-loop transmitantenna selection feedback from the radio communications network. 48.The communications terminal of claim 45, wherein the selection of thetransmit antennas is based on a closed-loop precoding feedback from theradio communications network.
 49. A method for selecting a transmitantenna of a communications terminal comprising a plurality of antennasand a selection circuit, for a transmission to a radio communicationsnetwork, the method comprising: determining, by the selection circuit,whether a selection criterion is fulfilled; and selecting at least oneantenna of the plurality of antennas as the transmit antenna if theselection criterion is fulfilled, wherein determining whether theselection criterion is fulfilled comprises comparing a transmissionpower of a transmit signal via the plurality of antennas beforeselecting the transmit antenna to the transmission power of the transmitsignal after selecting the transmit antenna.
 50. (canceled)
 51. Acommunications terminal, comprising: a plurality of antennas; and aselection circuit configured to select at least one antenna of theplurality of antennas as a transmit antenna for a transmission to aradio communications network based on a selection criteria, and acontroller configured to provide a block instruction to the selectioncircuit for blocking at least one further reselection of the transmitantenna by the selection circuit.